I just suggested it like that cause otherwise Marcus goes around likely unarmed. I mean, yang's got a bitching motorcycle, but she can't exactly bring that everywhere with her. I think the tank is more akin to an important possession rather than his Weapon of Choice. Though it does bring me to another LUDICROUS weapon idea!

A Cellphone/GPS device. It's got reception everywhere. Even internet access so you can research the weakness of your enemies and the information of your location anywhere you go! Also it has access to artillery turrets that you need to deploy preemptively (With Capsules). Not really great in PvP but super in teamfights when you need to deny an area to someone!